The purpose of this study was to document gamma diversity of Chironomidae in Outer Mongolia by documenting alpha and beta diversity of chironomids from streams sites within Gorkhi Terelj National Park and in the surrounding area. Pupal exuviae of Chironomidae were collected from streams using standardized, semi-quantitative sampling methods so that patterns in community structure could be compared to patterns in the study sites. Gamma diversity for the twelve sites in this study was 98 species, including 26 new records for Mongolia; alpha diversity of Chironomidae ranged from 3 to 37 species. Beta diversity ranged from 0–0.44 and mean beta diversity was 0.17. Species diversity did not correlate to distance between sites. The Chao 1 species estimator estimated 126 species of Chironomidae from the streams in Gorkhi Terelj National Park. Ad hoc analysis comparing chironomid communities from Gorkhi Terelj National Park and Lake Hovsgol area stream and lake sites increased the estimated number of species to 144. Dominant species were used in a double dendrogram analysis which yielded three distinct communities of chironomids which corresponded to three clusters of study sites that differed by habitat type, water quality, and physical characteristics. This study produced data for use in conservation of streams in Gorkhi Terelj National Park.